This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A191465 #36 Mar 31 2025 18:23:45
%S A191465 0,7,77,721,6545,59017,531377,4782841,43046465,387419977,3486783377,
%T A191465 31381057561,282429532385,2541865820137,22876792438577,
%U A191465 205891132061881,1853020188786305,16677181699535497,150094635296736977,1350851717672467801,12157665459055880225,109418989131510262057
%N A191465 a(n) = 9^n - 2^n.
%C A191465 a(n) is the number of words of length n over the alphabet {1,2,...,9} where at least one letter >= 3 appears. - _Joerg Arndt_, Jan 18 2024
%H A191465 Vincenzo Librandi, <a href="/A191465/b191465.txt">Table of n, a(n) for n = 0..300</a>
%H A191465 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-18).
%F A191465 a(n) = 11*a(n-1) - 18*a(n-2).
%F A191465 G.f.: 7*x/((1-2*x)*(1-9*x)). - _Vincenzo Librandi_, Oct 04 2014
%F A191465 a(n) = 7*A016133(n-1). - _R. J. Mathar_, Mar 10 2022
%F A191465 E.g.f.: 2*exp(11*x/2)*sinh(7*x/2). - _Elmo R. Oliveira_, Mar 31 2025
%t A191465 Table[9^n-2^n,{n,0,20}] (* _Harvey P. Dale_, Apr 16 2014 *)
%o A191465 (PARI) a(n)=9^n-1<<n \\ _Charles R Greathouse IV_, Jun 08 2011
%Y A191465 Cf. A016133, A016185, A118004.
%K A191465 nonn,easy
%O A191465 0,2
%A A191465 _Vincenzo Librandi_, Jun 03 2011